# First-Order Topological Quantum Phase Transition in a Strongly Correlated Ladder

## TL;DR

This paper uncovers a quantum tri-critical point in a strongly correlated fermionic ladder system where the topological phase transition switches from continuous to first-order, with clear local observable signatures.

## Contribution

It identifies a quantum tri-critical point in a strongly correlated 1D lattice system, demonstrating a switch in the topological transition's nature via DMRG simulations.

## Key findings

- Discovery of a quantum tri-critical point separating transition regimes.
- First-order topological transition characterized by local observables.
- Transition nature change driven by interaction strength.

## Abstract

We report on the discovery of a quantum tri-critical point (QTP) separating a line of first-order topological quantum phase transitions from a continuous transition regime in a strongly correlated one-dimensional lattice system. Specifically, we study a fermionic four-leg ladder supporting a symmetry-protected topological phase in the presence of on-site interaction, which is driven towards a trivial gapped phase by a nearest-neighbor interaction. Based on DMRG simulations, we show that, as a function of the interaction strength, the phase transition between the topological and the trivial phase switches from being continuous to exhibiting a first-order character. Remarkably, the QTP as well as the first-order character of the topological transition in the strongly correlated regime are found to clearly manifest in simple local observables.